Lens-grinding implement.



r BUOHHOP. LENS GRINDING IMPLEMENT.

APPLIGATION' FILED D110. 16, 1908.

- Patented 00132611909.

l mu mi i I l T UNITED T OFFICE.

FERDINAND BUGHHOP, OF NEW YORK, N.Y., ASSIGNOR TQ THE MEYROWITZ MANU-FACTUBING COMPANY, A CORPORATION OF NEW JERSEY.

To all whom it may concern:

Be it knownthat I, FERDINAND BUCHHOP, a citizen of the United States,residing at the city of New York, in the borough of Brooklyn and Stateof New York,. have invented certain new and useful Improvements inLens-Grinding Implements, of which the following is a full, clear, andexact description.

This invention relates to tools or apparatus employed in grinding thelens blanks for Kry tokbifocal lenses. In the manufacture 0 these lensesa depression or concavity is formed eccentrically in the surface of amajor lens blank at a point which must be accurately predetermined.Afterward a minor lens of glass of higher refractive power is fused intosaid depression or cavity, and the entire lens blank then ground awayand trimmed to form a lens for eyeglasses or spectacles inwhich adifferent focal length is obtained for distant vision from that obtainedin reading, the line of vision being downward in the latter case andcorrespond ing to the location of the minor lens blank. The nature ofthese processes and the subsequent character of use of the glassesnecessitate a somewhatprecise location and formation of the said cavityor-depression.

It is the main object of my invention to provide a combination of tooland workholding device which is adapted to do this work easily andexpeditiously for a plurality of lens blanks at a single operation.

The nature of the process and the characteristics of the tools, etc.,employed, embody several theoretical principles, as later pointed out. y

The structural characteristics of the ,invention will be firstconsidered, having reference to the accompanying drawin 's whichillustrate preferred embodiments of the invention.

In the drawings: Figure 1 is a sectional view showing a lens blank orwork-holder and grinding head, as employed in forming the depressions orcavities of Kryptok lenses in accordance with this invention; F ig,shows a similar couple adapted for a different radius of curvature ofthe depression; Fig. 3 is a bottom plan .view of the holder; Figs. 4:and 5 are sectional views showing slightly modified constructions; Fig.6 is a sectional view showing a further gnodifiv Specification ofLetters Patent' VII-VII of Fig LENS-GRINDING IMPLEMENT. i

Patented Oct. 26, 1909. Application filed December 16, 1908. Serial No.467,810.

cation, and Fig. 7 is a section on the line 6. i 1 designates a rarnehaving a central body 2 with a plurality of arms 3. These arms I haveinner faces adapted to support lens blanks in planes 4:, the essentialcharacteristics of which are that they all radiate at exactly equalangles from a-common axis and vertex; 7 and 9 to supportthe lens blankand which are-separated by an intermediate recess (3, and also a stop orshoulder 5 which fixes the radial location of the blank. Theconstruction of these various features is based on theoretical ormathematical considerations as follows:

The depressions or cavities C of the blanks A, being spherical incurvature, are necesapplicability when the entire surface of the blankis ground away to the prescribed curvature, it being merely necessary tocontinue the grinding until a surface of more than adequate dimensionshas been ground away on each blank. In grlndmg Kryptok lenses, theconditions are different, however,

.calling for a depression which is not only of certain curvature, butwhich is located in a predetermined position on a blank of prescribedform, and which must have a definite diameter determined by the depth towhich the grinding is carried. These conditions make it necessary toprovide for the various factors in some other way than merely cementingthe blanks more or less carelessly in any form of concave holder in theusual manner employed for ordinary lens work. To illustrate by apractical example, it may be assumed that depressions having aradius ofcurvature of one and thirteen sixteenths inches and a diameter across ofthree-quarters of an inch, are to be formed in lens blanks oftheordinary sort out from plate glass to a square out-line measuring aboutone and three-quarters inches on each side, the depressions beingcentered symmetrically For this purpose each arm has seats Thispriublanks might, of course, be independeiitly embedded in cement byindependent measuring and obtain the foregoing results,but the time andcare which would be necessary would be almost prohibitive for commercialpurposes. I make use of the following principles to expedite thelocation of the blanks, making the operation as simple or even simplerthan is the case in ordinary lens gr1nd- 111g processes.

A sphere coincident with the surface of the tool B may be circumscribedby an equilateral pyramid in which case the planes of each of the faceswill be tangent to the sphere. The points of tangency will furthermorebe located at equal and fixed distances from the apex of the pyramid.These distances are equal, but Vary with theradius of the tool or sphereand the vertical angle of the pyramid. In order to grind lens blankswith depressions in the manner described, they may be faced in theplanes of such a pyramid to determine their position in a work holder.There are other geometrical relations by which the lenses might belocated and centered, for example, by seating them inside a sphericalsurface of different curvature from the curvature of the tool, but Ihave found that the pyramid relation gives a very useful and practicalsolution fortperfectly mounting the lens blanks, as it enables everyfactor to be taken into account in a very easy way. The lens blanksbeing square and of plate glassof substantially uniform thickness,permits their being assembled on rigid seats which fix the planes planesof'such a pyramid, and inthis relation they may be easily locatedbylateral stops or shoulders on center lines of the pyramid faces and atexactly located distances'from the pyramid apex. Not-only, therefore,are the lens blanks easily located in all respects, but the grindingaction is insured to proceed in a way which is easily mathematicallypredetermined for a particular holder and tool.

In the example above noted a pyramid would first be theoreticallydetermined upon of such an angle as would permit an assembling of thesquare blanks with their side edges at a distance of about one andonequarter inches from the pyramid apex, which is substantially uniformdistance for all cases, being as compact a disposition of theblanks aspossible, limited by the proximity of their adjacent corners. Thiscompact disposition is desirable as it makes the pressure of thegrinding operation more nearly normal to the surface to be ground foreach blank. These conditions being determined upon, an easy mathematicalcomputation fixes the vertical angle of the pyramid at exactly foreadopted which will fix the planes of the 92. A lens holder isthereblanks-to be ground in the faces of the fore- I going pyramid at adistance of one and onequarter inches from its apex, the planes beingdetermined by rigid metallic seats of the holder which are adapted to beeasily fitted to suit the particular vertical angle of the pyramid.

Referring now again to the practical construction, Figs. 1 and 2 showthe adaptation of the lens holder to two different grinding heads B andB, respectively. Grinding head B has a radius of curvature of one andthirteensixteenths inches and grinding head B has a radius of curvatureof one and eleven-sixteenths inches. The ledges 5 being located at asubstantially constant point in accordance with the foregoing principlesfor all cases, it follows that the planes t in Figs. 1 and2 (which areparallel with the front faces of the blanks owing to the latter being.of plate should make angles of tank simple bevel angle-gage so that theplane de- Q termined by this ledge and the support 7 is exactly -16 inFig. 1 and 14 in Fig. 2. The

machinii'ig being accomplished in this simple of their faces to beground, accurately 1n the 1 way, it is merely necessary to mark theholder to accord to the particular grlnding head for which it wasdesigned, and thereafter any comparatively unskilled operator can easilyand expeditiously assemble the lens blanks against the seats 5, 7 and 9and pour the usual cement into the recess 6 and insert the apparatus ina grinding machine without further attention, whereupon the lens blankswill be pro erly ground with depressions exact in matters of form,curvature, diameter and location, these factors all being determined bythe action of the machine on account of the foregoing theoreticalprinciples with respect to the pyramid which is virtually formed in,-.con-

mined radius.

In Figs. 4 and 5 and varied in a dlfferent way. In Fig. 4

- the holder has pivoted arms 10, the position of which is fixed byadjustment screws 12 and which have flat faces '11 to receive the lensblanks. In Fig. 5 pivoted arms 13 are provided with stems 1 engaged by acentral plug 15', the position of which is varied by a threaded stem 16and lock nut 17. 18 deunction with the spherical tool of deterthe planesare determined In Fig. 6 the lens the flat faces of the holder by clamps2O having bent-over ends 21 to: engage the lens blanks and tightenedthereon by set screws 22.

. Having described my invention, I claim 1. A lens grinding implementcomprising a work holder having a plurality of seats therein for lensblanks in combination with a spherical grinding head ofrsuch curvaturethat it will be tangent to eccentric points on all of the lens blanks.

2. A lens grinding implement comprising a holder having seats for aplurality of'lens blanks, of a spherical curvature tangent to thesurfaces "of the lens blanks at point's'ofiset from the centers of saidblanks by -a predetermined distance.

3.v A lens 7 a' holder having seats for; a plurality of lens blanks, incombination with a grinding head' of a spherical curvature tangent tothe surfaces of the lens blanks at, points offset from the centers ofsaid blanks by a predetermined distance toward a common'point or vertex.

' i. A lens blank holder forgrinding processes, comprisin a frame havingarms projecting symmetrically at equal angles from a common central axisand vertex and having interior'faces on which the lens blanks areaccurately seated in ithe planes of said angl 5. esses, comprising-afraine havmg arms projecting symmetrically at equal angles from blanks mheld against in combination with a grindinghead inding. implementcomprising es v.

A lens blank holder for grinding proe a common central axis and vertex,said arms having. interior faces on which the lens blanks are accuratelyseated in the planes of said anglesand having lugs or shoulders to 1 rlocate said blankson said faces.

6. A lens blank holder for grinding processes, comprising a frame havingarms pro-v jecting symmetrically at equal angles from a common centralaxis, said arms having interior faces with a recess Y or cavity and"adapted to seat lens blanks accurately in the planes of said angles.

7-. A lens blank holder for grinding processes, comprising-a framehaving arms pro- Jectmg symmetrlcallyat equal angles from a commoncentral ax s, said arms having 111-.

terior faces to seat the blanks accurately in the planes of said angles,and having lugs to position said blanks accurately at equal distancesfrom said axis.

8. A lens blank holder for grinding processes,1comprising a frame havingarms projecting symmetrically at equal angles from a common centralaxis, each arm having a ledge and a rounded extremity adapted toposition the blanks accurately in the planes of said angles; said armshaving a recess between said ledges and said extremities whereby theledges may be cut away and, effect a change in the angles of the lensblanks.

In witness whereof, I subscribe my signa ture, in the presence of twowitnesses.

: FE DINAND/BU HH P,

wanes s's WM. Scroomsnmen, WALDO CHAPIN.

